Heat exchangers



R. POUIT HEAT EXCHANGERS Nov. 3, 1964 Filed April 26 1961 2 Sheets-Sheet 1 FIGS INVENTOR ROBERT POUIT ATTORNEY United States Patent 11 Claims. ct 165-6) The present invention relates to heat exchangers and methods of making the same, more particularly to devices of the type providing direct calorific transfer by means of movable heat-conveying elements.

Among the objects of the invention is to generally improve the effectivness of apparatus of the type mentioned and to reduce the weight and overall size thereof.

The principle is already known which governs heat exchanger apparatus of the type essentially constituted by movable elements circulating continuously inside two chambers respectively containing the fluids which flow through the said chambers and between which the exchange of heat takes place, in such manner that the said elements, which are reheated as they pass into that chamber through which the fluid flows at the highest temperature, give up the heat conveyed by them to the fluid in the chamber which has the lowest temperature. In numerous applications in which apparatus of the type mentioned is employed, as in the case of gas turbines, for example, the fluids flow at very difi'erent pressures, thereby resulting both in losses due to deficiencies in fluidtightness and at the same time in more or less substantial losses of pressure in the fluids in circulation.

A method has already become known which consists in using as heat transfer elements endless strips moving in a closed circuit through a pair of fluid chambers so as to form, by superposition, material nests which are gripped between rollers at the inlet and at the outlet of the chambers inside which the fluids flow at diiferent pressures and temperatures.

An important object of the present invention is the provision of improved means in connection with a heat exchanger of this type to ensure coordination of movement or spacial stability of the movable heat-conveying strips or elements.

Another object of the invention is the provision of multiple units or groups of movable elements in a heat exchanger of the type mentioned, including means to operate and synchronize the movements of the elements of each unit with each other and with the elements of the remaining units of the composite heat exchanger structure.

Yet another object of the invention is the provision of a heat exchanger of the above type comprising a plurality of units or groups of nested endless heat transfer elements or strips operated by a common drive means and embodying improved means to stabilize and synchronize the movements of the elements of each group with each other and with the elements of the other groups of the composite heat exchanger structure.

With the foregoing objects in view, the invention involves generally the forming of the heat-conveying endless strips with teeth providing a continuous rack along at least one of the edges of the nests of the strips, said rack cooperating with at least one rotatable pinion to coordinate or stabilize the movements of the strips, in such a manner as to ensure the strips to be uniformly spaced from each other while moving through the fluid chambers of the heat exchanger between which heat transfer is to be effected.

According to an improved feature of the invention the entire thermal transfer device may be constituted by a plurality of multiple units or sets of nests or groups of endless strips of heat-conveying material, said sets or groups being advantageously driven by a common drive 3,155,151 Patented Nov. 3, 1954 means and synchronized by a common pinion or aggregate of pinions cooperating with the rack teeth of adjacent units or groups of the composite heat exchanger structure. In a heat exchanger of this type, the coordinating or stabilizing pinions may serve as driving means for the units by connection with a suitable prime mover, such as an electric motor, or alternatively, the units may be driven by way of one of the friction pressure rollers common to all of the units, in which case the pinion coupling means between adjacent units merely serve to stabilize or synchronize the movements of the strips of the groups or units, thereby reducing wear of both the teeth of the strips and the pinions and resulting in increased life of the heat exchanger. Furthermore, in the operation of the multiple heat exchanger units, the strips of the different units may be either driven in the same direction or in opposite directions with the pinion coupling means between adjacent units serving to stabilize both the movements of the strips of the individual units and the movements of the strips of the different units of the heat exchanger, as will become further apparent as the following description proceeds.

Another improved feature of the invention relates to the provision of heat traps such as in the form of a number of spaced cuts in the longitudinal direction of the heat-conveying strips or elements, to prevent heat dispersion laterally or at right angle to the movement of the strips and to thereby improve the efficiency of the heat transfer between the fluid chambers of the heat exchanger.

The invention, both as to its ancillary objects and novel aspects will be further understood from the following detailed description taken in conjunction with the accompanying drawings forming part of this specification and wherein:

FIG. 1 is a cross-section taken along the line II of FIG. 2 illustrating a heat exchanger constructed in accordance with the principles of the invention;

FIG. 2 illustrates the apparatus of FIG. 1 in horizontal cross-section;

FIG. 3 illustrates a transfer strip in which are formed non-continuous cuts in accordance with the invention; and

FIG. 4 illustrates in perspective an alternative form of construction of a heat exchanger according to the invention.

Like reference characters denote like parts in the ditferent views of the drawings.

Referring to the drawings, FIGS. 1 and 2, in a frame 1,

separated into two compartments 2 and 3 by a central portion 4, forming with said compartments two passageways 5 and 6, the said frame 1 being closed by two covers 7 and 8, there is employed a certain number of endless strips 9 of metal or other heat-conveying material of high specific heat characteristics, having diiferent lengths and being disposed successively one within the other so as to form substantially equidistant loops in the compartments 2 and 3. In the passageways 5 and 6, the strips 9 are juxtaposed, and fluid-tightness is ensured between the two compartments 2 and 3 in the passageways 5 and 6 by gripping the nest of strips 9 together at these places, between two pairs iii-11 and 12-13 of rotating rollers, the shafts 14 of the rollers 10 and 12 being centered, for example, by means of ball-bearing 15 carried by the frame 1 or by the covers 7 and 8 of the said frame. The shafts or spindles of the rollers 11 and 13, which co-act respectively with the rollers 10 and 12, can be displaced in elongated slots 16 under the action of springs 17 and, as a result of the gripping action of the rollers 10-11 and 1213 against the strips 9, thereby ensure fluid-tightness between the compartments 2 and 3 in which, as an example, the hot gases to be cooled (compartment 2) and the compressed air to be re-heated (compartment 3) re-v spectively circulate.

A part of these arrangements, such as the fluid-tightness ensured by means of rollers is already known and has been descriebd solely for the sake of clarity of the description.

Before giving an exact description of the means which more especially characterize the present invention, it must be noted that the different strips 9, at the places in which they are gripped between the rollers -12 and 12-13, must be tightly applied against each other without slipping, failing which their end loops in the compartments 2 and 3 would no longer remain equidistant and could even rub against each other and similarly against the internal walls of the heat-exchanger body, the effect of which would be on the one hand to disturb the thermal flow and on the other hand to result in wear of the strips.

It must further be noted that, in order to ensure the maximum eifectiveness of the apparatus, the heat yielded in the compartment 2 to a band having a width a located at the distance I: from the upper edge of the strips 9 by the hot gases which circulate along the path of the arrow A, must necessarily be conveyed on the same band having a width a at the same distance it from the upper edge of the strips 9 so as to be given olf in the compartment 3 to the air to be reheated which follows the path of the arrow B, without thereby resulting in any appreciable upper dispersion of this heat in the mass of the strips during the time taken by the said strips to complete a half-revolution.

In accordance with the invention, and in the example of construction which is illustrated in FIGS. 1 and 2, the stability in space of the nest of strips 9 is ensured by forming notches in at least one of their edges in the shape of the set of teeth of a toothed rack which is adapted to engage with pinions 13, at least one of which is set into rotation by a motor so as to drive the nest of strips 9.

As shown in FIG. 1, it is preferable to split-up the nest of strips 9 into two elements and to ensure that the two nests which have thus been split-up are driven in opposite directions by the same pinions 18. The teeth which are engaged also ensure fluid-tightness between the compartments 2 and 3, on the oppositely facing horizontal edges of the nests of strips 9.

In this case, as is shown in FIG. 1, the frame 1 is provided half-way up with a partition 19 in which are formed communication openings 2% and 21 which are preferably displaced with respect to the inlets 22 and 23 of gas and compressed air as well as with respect to the gas and air outlets 24 and 25.

The splitting-up of the nest of strips 9 into two elements already limits the dispersion of heat in the metal of the strips, in a direction at right angles to their movement. In order to limit this dispersion still further, and in accordance wtih the invention, cuts 30, FIG. 3, are made in the metal of the said strips 9, preferably in the direction of their displacement, these cuts 34! being naturally interrupted in the vincinity of the extremities of each strip.

A description will now be given below with reference to the alternative form of construction which forms the subject of FIG. 4.

This second form of construction incorporates improvements in construction which are especially intended to reduce the wear of the teeth formed on the edge of the strips as well as to stabilize in space the paths described by each point of these metallic strips as they move in a closed circuit.

In this second alternative form of construction, the heat exchanger body has not been illustrated, for purposes of greater clarity. The endless metallic strips are again designated by the reference 9, while 10 and 12 designate the rollers which press the said strips together, loaded by a spring 17 and with which, in this form of construction, a single internal counter-roller 11 cooperates.

As is the case in the first fon'n of construction, there is formed on the oppositely facing edges of the endless strips 9 a set of teeth 31 by means of which the said strips engage with two pairs of pinions 18:1,18b and 18a and 181) having the same number of teeth, in the two zones in which the said strips are pressed together between the rollers 1t}, 11 and 12, the two pinions of each pair also engaging with each other.

The co-axial pinions 18a, 13a and 18b, 18b rotate in opposite directions. It follows as a result of this arrangement that the two conjointly operated nests of strips 9 move in the same direction as indicated by the arrows x of HG. S, and not in contrary directions as in the form of construction in accordance with FIGS. 1 and 2, which in no way affects the operation of the apparatus.

In accordance with this alternative form of construction, means are again provided to synchronize the rotation of both pairs of pinions, in such manner as to ensure the perfect fixity in space of the path of the strips, the nests of which must remain symmetrical with respect to the longitudinal and central vertical plane of the exchanger, For this purpose, the top pair of pinions 18a and 18b is positively coupled to the corresponding bottom pair of pinions 18a, 18b in the following manner, in the case of the example considered.

An intermediate shaft 32 carries at each extremity a toothed pinion 33-33 keyed on the said intermediate shaft. The pinion 18b is rigidly coupled to another coaxial pinion 34 with which the pinion 33 engages. Similarly, the pinion 18a is rigidly coupled to another 00- axial pinion 34 which engages with the pinion 33'. An equipment unit of this kind ensures the perfect synchronism of rotation of the pinions 18, 18b and 18a, 18b, and consequently ensures the strictly equivalent linear displacement but, in opposite directions, of the upper and lower length of each nest of strips 9.

Such a movement of rotation of both nests of strips in the same direction makes it possible to drive the said strips by means of a single common device, irrespective of the number of successive nests which the heat exchanger comprises, in the direction of flow of the fluids shown by the arrows y. The practical value of this second arrangement consists in the fact that the relatively fragile teeth 31 of the strips are unsubjected to the driving effort proper, since the said teeth no longer have any function other than to operate conjointly the opposite displacements of the upper and lower lengths of the nests of strips.

In the example of construction shown in FIG. 5, it is preferably the inner pressure roller 11, against which the nest of strips 9 is applied elastically as a result of the force of the spring 17 acting upon the outer rollers 19 and 12, which, as a result of friction, transmits to the said nest the rotation which is imparted to the said roller 11 by any desired means, not shown in the drawings. To this end, each roller 10 corresponding to each nest of strips rotates with the shaft 35 which is guided in stirrup-members 36, these latter being slidably mounted in the body of the apparatus, which is in this case shown only by a fixed cross-piece 37. Through the intermediary of a lever 38 which is pivotally mounted at 39 on the said cross-piece and which is engaged in a corresponding slot in the stirrup-member 36, the spring 17 transmits to the shaft 35, and consequently also to the rollers 15), the force of application which is necessary for pressing the strips 9 between the rollers 10, 11 and 12 and for driving the said strips by friction.

In the foregoing the invention has been described in reference to a specific illustrative device. It will be evident however, that variations and modifications, as well as the substitution of equivalent parts or elements for those shown herein for illustration may be made in accordance with the broader scope and purview of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.

I claim:

1. In a heat exchanger, a casing having a pair of chambers for passing different pressure fluids, heat transfer means comprising a plurality of heat conveying endless flexible strips movable in closed circuits between said chambers, said strips being of progressively decreasing length and arranged in edgewise and nested position Within each other, friction roller means resiliently compressing the nests of the strips in the region between said chambers, at least one of the edges of said strips being formed with continuous teeth, to provide a pair of racks defined by the aligned teeth of the compressed strips within said region and at least one rotatable pinion engaging one of said racks, to coordinate the movements of said strips and to maintain the same in substantially uniformly relative spaced position from each other within said chambers.

2. A heat exchanger as claimed in claim 1, said strips being driven via said pinion forming an etfective driving means.

3. A heat exchanger as claimed in claim 1, said strips being driven via said roller means forming an efiective driving means.

4. A heat exchanger as claimed in claim 1, said strips being provided with spaced linear cuts forming heat traps and extending in the longitudinal direction of the strips.

5. In a heat exchanger, a casing having a pair of chambers for passing different pressure fluids, heat transfer means comprising a plurality of groups of heat conveying endless flexible strips movable in closed circuits between said chambers, the strips of each said groups being of progressively decreasing length and arranged edgewise and nested within each other with the groups of nested strips being axially aligned with each other, common friction pressure roller means to resiliently compress the strip portions of the nests of each said groups inthe region between said chambers, at least one of the edges of the strips of each group being formed with continuous teeth, to provide a pair of racks defined by the aligned teeth of the compressed strips Within said region and pinion coupling means engaging and operatively interconnecting the racks of adjacent groups of strips, to coordinate the movements of the strips of each group and to synchronize the movements of the strips of all the groups of said heat exchanger.

6. A heat exchanger as claimed in claim 5, said strips being driven via said coupling means forming an effective driving means.

7. A heat exchanger as claimed in claim 5, the strips of each said groups being driven in common and in the same direction by said friction roller means as an effective driving means, and rotation reversing means embodied in said coupling means.

8. In heat exchanger, a casing having a pair of chambers for passing different pressure fluids, heat transfer means comprising a plurality of groups of heat conveying endless flexible strips movable in closed circuits between said chambers, the strips of each group being of a progressively decreasing length and arranged edgewise and nested within each other with the groups of nested strips axially aligned with each other, a common internal friction pressure roller and a pair of cooperating external spring-urged rollers to resiliently compress the nests of the strips of each group in the regions between said chambers, at least one of the edges of the strips of each group being formed with continuous teeth, to provide a pair of racks defined by the aligned teeth of the compressed strips within said region, and pinion coupling means engaging and operatively connecting the racks of adjacent groups to coordinate the movements of the strips of each group and to synchronize the movements of the strips of one group with the movements of the strips of the other groups.

9. A heat exchanger as claimed in claim 8, the strips of all said groups being driven in the same direction by said internal roller forming an effective driving means, and said coupling means consisting of a pair of pinions in engagement with one another and each engaging the teeth of one of the half portions of the strips of adjacent groups moving in the same direction.

10. A heat exchanger as claimed in claim 8, the strips of all said groups being driven in the same direction by said internal roller forming an effective driving means, and said coupling means consisting of two pairs of pinions arranged with the teeth of each pair in meshing engagement with one another and with the teeth of different half portions of said strips of adjacent groups moving in the same direction.

11. A heat exchanger as claimed in claim 10, including further pinion coupling means including rotation reversing means and operatively engaging one of the pinions of said first pair and one of the pinions of said second palr.

References Cited in the file of this patent UNITED STATES PATENTS 2,866,624 Hulmquist Dec. 30, 1958 2,888,248 Bubniak et a1 May 26, 1959 2,938,713 Collman May 31, 1960 

1. IN A HEAT EXCHANGER, A CASING HAVING A PAIR OF CHAMBERS FOR PASSING DIFFERENT PRESSURE FLUIDS, HEAT TRANSFER MEANS COMPRISING A PLURALITY OF HEAT CONVEYING ENDLESS FLEXIBLE STRIPS MOVABLE IN CLOSED CIRCUITS BETWEEN SAID CHAMBERS, SAID STRIPS BEING OF PROGRESSIVELY DECREASING LENGTH AND ARRANGED IN EDGEWISE AND NESTED POSITION WITHIN EACH OTHER, FRICTION ROLLER MEANS RESILIENTLY COMPRESSING THE NESTS OF THE STRIPS IN THE REGION BETWEEN SAID CHAMBERS, AT LEAST ONE OF THE EDGES OF SAID STRIPS BEING FORMED WITH CONTINUOUS TEETH, TO PROVIDE A PAIR OF RACKS DEFINED BY THE ALIGNED TEETH OF THE COMPRESSED STRIPS WITHIN SAID REGION AND AT LEAST ONE ROTATABLE PINION ENGAGING ONE OF SAID RACKS, TO COORDINATE THE MOVEMENTS OF SAID STRIPS AND TO MAINTAIN THE SAME IN SUBSTANTIALLY UNIFORMLY RELATIVE SPACED POSITION FROM EACH OTHER WITHIN SAID CHAMBERS. 